The present invention relates to a method of manufacturing shaped bodies, in particular plates, from particles having a surface with a wax layer, in particular straw, hemp stalks, maize stalks, grapevine stalks or the like, which are scattered to form a mat and subsequently pressed to form the shaped body.
A method of this kind is known from DE-OS 3 021 455. In this method, the particles are first comminuted by chopping in a first process step, whereupon they are split up into chip fibers in a second, subsequent step.
In a further subsequent process step, the chip fibers are dried, whereupon the dried chip fibers are admixed with a binder and a paraffin emulsion.
The particles which have been coated with glue in this way are further comminuted in a further process step, with the further comminution of the glue-coated particles being important to the method described in this publication. It is namely specified that the number of those particles surfaces which have an unfavorable effect on the later bonding during the pressing of the mat are substantially reduced by said further comminution of the glue-coated particles. At the same time, the binder is distributed even better to all now present surfaces of the particles, and thus further homogenized, during the further comminution due to the smearing effect known from chip gluing.
While boards with good strength properties are generated with the method described in DE-OS 3 021 455, a relatively high binder content and the addition of a paraffin emulsion is required. Furthermore, a relatively large number of separate process steps are required, with each process step increasing the costs of the process.
It is the object of the invention to develop a method of the kind first mentioned such that the required proportion of binder can be reduced and the number of required process steps reduced.
This object is satisfied in accordance with the invention starting from a method of the kind first mentioned by the particles first being comminuted in a single process step, being heated in a following process step and further comminuted in a subsequent process step and a binder begin finally admixed with the further comminuted particles.
It has surprisingly been found that, on the one hand, a separate process step to split up the comminuted particles subsequent to the first comminution process can be dispensed with if, in accordance with the invention, the comminuted particles are first immediately heated, then further comminuted and only then admixed with a binder. On the other hand, with this procedure, the quantity of binder required can be reduced with respect to the known methods without impairing the strength properties of the plates generated.